1. Technical Field
This invention generally relates to milking apparatus that use milking liners to draw milk from the teat. More particularly, the invention is related to the vent used with the milking liner. Specifically, the invention relates to anti-clogging vent plugs that may be selectively installed into and removed from milking liners.
2. Background Information
Automatic milking machines have been used to extract milk from different mammals through most of the past century. Most of these machines include a claw that typically has four nipples that are connected to teat cup assemblies that are attached to the teats. The teat cup assemblies include a rigid (hard plastic or metal) shell with a resilient, elastomeric milking liner (also known as a milking inflation) disposed within the shell. A short milk tube extends from the liner. A vacuum source is applied to the short milk tube and an alternating vacuum is applied to the shell to cause the liners to collapse and expand and thereby massage the teats and suck milk from the teats. The milk flows from the liners, into the short milk tube, to the nipples of the claw, and from there through a conduit to a collection tank.
The liner is one of the few components of an automatic milking machine that comes into direct contact with the cow. Liners collapse and expand to massage the teat to cause milk to flow. Liner performance may be maximized with the proper pulsation ratio. Numerous milking inflation designs have been developed for collapsing on the teat in different manners. The art desires an inflation having an open, relatively large, readily collapsible barrel that uniformly collapses around the teat to provide effective and comfortable milking. The structure of the barrel should provide a reliable collapsing configuration and a long useful life. Liners that collapse and expand slowly are undesirable. Liners that pinch or otherwise irritate the teat are also undesirable.
Air vents are also used with liners. The air vents are used to prevent the milk in the barrel or short milk tube of the liner from being drawn back towards the teat when the liner expands. An exemplary vent plug is shown in U.S. Pat. No. 6,055,931. A drawback with these types of vent plugs is that the air inlet opening is exposed to the environment under a cow and is frequently clogged by splattering debris (such as manure) from the floor in the milking parlor. Although the clog resistant air vent plug shown in U.S. Pat. No. 6,055,931 is effective, the art desires additional air vent plug designs that do not clog.